Re: Just about

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Mddeming-at-aol-dot-com 

In a message dated 5/5/04 10:43:02 AM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:
 > first, I would consider
 > losing your entire primary design... Stick with a
 > flat pancake design

 > the primary
 > should be a flat spiral at the base of the
 > secondary

Got it. but what exactly should I do? is it crucial,
and cant I just modify my existing primary?

     A flat spiral is more effective, giving better performance, sparkwise. 
But, if you want to keep your basic design for aesthetic reasons, there are 
several improvements you can make.  You can improve your existing helical 
primary by greatly reducing the space between turns to 20-25 mm center to 
center. This will greatly reduce the arcing between coils. a piece of 
plastic pipe as a collar between the primary and secondary will also help. 
It should be slightly taller than the now-shortened primary. you may also 
want to consider a plastic ring glued on the top of the collar which allows 
the secondary to pass through, but shields the top of the primary from 
downward directed hits.
     Any sharp metallic points on or near the primary or secondary will be 
a source of corona losses. The ties between primary and frame should be 
plastic cable ties, if possible. other non-conductive materials such as 
fishing line, may also be used.
     A lot depends on the purpose(s) to which you will put your coil. 
Modern coil design is optimized for maximum spark length, i.e., a display 
tool (or toy). In the early days of Tesla coils many were HV/RF 
transformers to supply power to other devices (X-ray machines, etc.)and 
streamers were as undesirable byproduct. Horizontal coils with helical 
primaries and small terminals were preferred for these applications.

 > Place a safety gap across your NST.  A piece of
 > wire
 > from each NST terminal to the NST case, with about
 > 1/4 inch spacing
 > between
 > the two, should suffice.

Terry Fritz mentioned it to me once... what exactly
should I do and with which terminals (even the input)?
And is it crucial, cant I simply locate a peace of
plastic shielding my NST?

Plastic shielding may protect from external strikes, but the safety gap is 
for internal problems. Transients occurring in the tank circuit through 
mis-fires , etc., can send HV spikes of energy back into the transformer 
and kill it internally. Plastic shielding will do nothing for this.

 > And to answer your grounding question, ground
 > the
 > NST and the bottom of the secondary to a pipe driven
 > into the ground

That's just about what I've figured, but should I
connect both groundings to the same pipe? and should I
ground the NST through its 'normal' grounding?

 > if you have holes in your
 > PVC, this is bad,
 > especially if wire goes through it

The holes are in the parts of the PVC that are not
coiled, such as the plastic caps at the end or the
PVC's body at the bottom (Like shown in pictures at my
web page). Is it still a problem?

Holes at the extrema of the PVC are not bad unless you have wire going 
through them to the inside. Wire inside the ends of the column are 
extremely bad as they will encourage internal arcing that you may not see 
until much damage is done. Keep all wiring on the outside surface.

Spherical terminals can be used, but they should be 2-4 times the diameter 
of the secondary.

Thanks again, Nir

Shalom,

Matt D.